Turbines and pumps are used for various purposes, and may have similar designs, with the most significant differences being the direction of flow of fluid through the device, and whether the device requires an energy input or provides an energy output. Turbines are used to convert kinetic energy of a fluid to a rotational energy in a shaft. The rotational energy may then be used to perform work, and particularly may be used to generate electricity. Pumps are used to move fluids, and in particular are used to move fluids against a back pressure. In short, pumps convert mechanical energy into hydraulic energy, while turbines convert hydraulic energy into mechanical energy.
One application of a turbine is to recover energy from a natural gas processing operation. Natural gas may have significant quantities of waste gases when recovered from a well, and may need to be cleaned in order to be transported, sold, or used. One method of cleaning natural gas (also referred to as sweetening) is to combine it with water and amine in a high pressure environment. This process allows the separation of the high quality natural gas from the waste gas or gases. After this process, the natural gas may be transported to a lower pressure environment for storage or transport.
Creating the high pressure environment for the cleaning of natural gas is an energy intensive process. The lean amine/water mixture is injected into the high pressure environment (also referred to as a contactor) at high pressure. The contaminant gases (specifically, CO2 and H2S) are then absorbed by the amine/water mixture, and the now rich amine/water mixture flows out of the contactor where its pressure is reduced to atmosphere. Traditionally this is done using a backpressure valve. The present application proposes replacing this valve with a turbine.
Natural gas recovery operations often involve natural gas having a large amount of debris in the gas. Therefore pumps and turbines used in this process must have high tolerances for debris and foreign matter, especially the bearings in pumps and turbines that are process lubricated. Process lubricating pumps and turbines use the same fluid that is flowing through the device to lubricate the pump or turbine.